Lecture 14 10/23/24 Flashcards
What are the characteristics of Rhodococcus equi?
-gram-pos pleomorphic rods
-Chinese character formations
-facultative intracellular pathogen
-soil organism
-harbored in intestinal tract of adult herbivores
-inhaled or ingested
-seen in 1-6 month old foals
-insidious disease (gradual)
What are the clinical manifestations of Rhodococcus equi?
-chronic suppurative pneumonia
-anorexia
-lethargy
-fever
-nasal discharge +/- cough
-tachypnea
-dyspnea
-nostril flaring
-abdominal breathing
What are the extra-pulmonary manifestations of Rhodococcus equi?
*intestinal manifestations:
-possibly subclinical
-ulcerative colitis
-typhylitis
-suppurative inflammation of colonic/mesenteric lymph nodes
*polysynovitis
*panophthalmitis
*guttural pouch empyema
*sinusitis
*pericarditis
*hepatic and renal abscessation
What findings are seen on bloodwork with Rhodococcus equi?
-hyperfibrinogenemia
-neutrophilic leukocytosis +/- monocytosis
What findings are seen on radiographs with Rhodococcus equi?
-alveolar pattern
-regional consolidation and/or abscessation
Which methods are used to diagnose Rhodococcus equi?
-TTW with cytology and bacterial culture
-PCR
What are the characteristics of antibiotic treatment for Rhodococcus equi?
-erythromycin + rifampin
-given for 4-10 weeks
-can use azithromycin or clarithromycin
What are the side effects of antibiotic treatment of Rhodococcus equi?
-idiosyncratic hyperthermia and tachypnea
-self limiting fecal softening
-Clostridium difficile enterocolitis in mares exposed to the macrolides
What are the supportive treatments for Rhodococcus equi?
-oxygen support
-hyperbaric oxygen
-IV fluids
-nutrition support
-monitoring of fibrinogen
-radiographs/ultrasound for monitoring
What is the prognosis of Rhodococcus equi infection?
-treatment is very successful
-poorer prognosis with extra-pulmonary manifestations of disease
-decreased chance of racing as an adult, but performance in those racing not reduced significantly
What are the surveillance strategies for Rhodococcus equi?
-daily rectal temps
-fibrinogen levels measured every 2 weeks
-WBC count measured every 2 weeks
-ultrasound every 2 weeks (detects peripheral lesions only)
How is Rhodococcus equi controlled?
-avoid high animal density
-avoid sandy/dusty soils and manure laden areas
-pasture rotation
-plant or irrigate dusty paddocks/pastures
-surveillance strategies
-hyperimmune plasma
-prophylactic administration of azithromycin
What are the terms used for moderate/severe and mild equine asthma?
moderate/severe: recurrent airway obstruction/RAO
mild: inflammatory airway disease/IAD
What are the characteristics of equine asthma?
-naturally occurring
-periods of reversible airway inflammation
What causes the clinical signs of equine asthma?
-neutrophil accumulation
-mucus production
-bronchospasm
What is the impact of equine asthma on the lungs?
-decreased compliance
-increased resistance
-increased work of breathing
-arterial hypoxia
What is the epidemiology of equine asthma?
-seen in horses that are stalled and fed hay
-increased incidence with age
-familial tendency
What is the pathophysiology of equine asthma?
-inhalation of dusts and molds increases IL-8 production
-neutrophil accumulation leads to small airway obstruction
-mucus accumulation, bronchospasm, and inflammatory changes in airway walls increase small airway obstruction
-obstruction leads to V/Q mismatch (poor vent., normal perfusion)
-inefficient gas exchange leads to hypoxia
-horses increase resp rate to compensate, but tidal vol. remains the same
-abnormal breathing pattern occurs
What is the typical history of a horse with equine asthma?
-stalled and eating hay
-coughing
-decreased exercise tolerance
-prolonged recovery from exercise
-nasal discharge
-resp distress
What are the clinical signs of equine asthma?
-cough
-nasal discharge
-flared nostrils
-increased resp rate
-rapid inspiration and forced prolonged expiration
-weight loss
-increased effort of breathing
-heave line
What can be heard during auscultation in horses with asthma?
-can be quiet
-increased breath sounds
-crackles and wheezes
-tracheal rattle
What findings can be found on arterial blood gas in horses with asthma?
-chronic respiratory acidosis
-hypoxemia
*depends on magnitude of resp compromise
What is the primary finding on BAL in equine asthma?
non-degenerate neutrophilic inflammation
What are the findings on radiographs in equine asthma?
-increased bronchovascular and interstitial changes
-lung hyperinflation
What is an atropine or buscopan test?
short lived broncho-dilator administration to determine if patient symptoms improve
*associated with development of ileus
What are the options for allergy testing in horses?
-serum
-intradermal
What are principles of equine asthma control?
-environmental control
-reduce inflammation
-relieve resp distress
Which components of environmental control are important for equine asthma?
-house horses 100% outdoors
-bedding
-diet
How can inflammation be reduced in equine asthma?
-NSAIDs
-inhaled or systemic corticosteroids
Which systemic corticosteroids are used in equine asthma?
-dexamethasone: short acting and easily withdrawn
-prednisolone: less side effects
-triamcinolone: long acting
What are the characteristics of systemic corticosteroids for equine asthma?
-oral or injectable
-more side effects since acting systemically
-lowest possible dose is used
-help to prevent airway remodeling
Which inhaled corticosteroids are used in equine asthma?
-beclomethasone
-fluticasone
What are the characteristics of inhaled corticosteroids for equine asthma?
-use metered dose inhalers
-not systemic, less side effects
-not for initial or emergency use; require animal to take deep breaths
Which classes of bronchodilators are used to relieve resp distress?
-anticholinergics
-beta-2 adrenergic agonists
-methylxanthines
What are the characteristics of atropine?
-anticholinergic
-IV
-ileus and excitement with repeat doses
What are the characteristics of ipratropium?
-anticholinergic
-inhalation
-no side effects
What are the characteristics of clenbuterol?
-beta-2 agonist
-given oral or IV
-only FDA approved bronchodilator for horses
What are the characteristics of albuterol?
-beta-2 agonist
-given oral or IV
-not well absorbed orally in horses
What are the characteristics of theophylline?
-methylxanthine
-oral
-erratic absorption and narrow therapeutic index
What are other potential treatments for equine asthma?
-mucolytic drugs
-antihistamines
What are the steps to prevention of equine asthma?
-provide clean, well ventilated housing
-properly treat and manage resp disease
What is the prognosis of equine asthma?
-dependent on disease stage
-unknown if chronic airway remodeling can be reversed
-important to prevent recurrence of airway inflammation
-expensive to maintain lung health
